As part of the Federal Railroad Administration’s locomotive cab occupant protection research, a Secondary Impact Protection System (SIPS) for locomotive engineers was developed. The system uses an automotive-style passenger airbag and a deformable knee bolster to provide the desired protection – without compromising the normal operating environment and egress. 

A prior version of the system was prototyped and tested under a dynamic sled test with a 23g crash pulse and was shown to meet limiting human injury criteria in the Department of Transportation’s Federal Motor Vehicle Safety Standards (FMVSS 208) for the head, chest, neck, and femur. Due to marginal performance for the chest injury index, an improved SIPS design was pursued. The major improvements were slightly larger airbag with two additional vents, higher-capacity inflators self-contained within the airbag module, a knee bolster system with thicker knee plate, and brackets shifted toward the front edge of the desk. 

Simulations followed by the sled testing confirmed the SIPS successfully met all 11 criteria of the FMVSS 208, demonstrating excellent occupant protection for an unbelted locomotive occupant in a severe frontal collision.